diff --git a/lib/capybara/rack_test/form.rb b/lib/capybara/rack_test/form.rb
index 43ce2e60d..91455dd7b 100644
--- a/lib/capybara/rack_test/form.rb
+++ b/lib/capybara/rack_test/form.rb
@@ -13,6 +13,8 @@ def initialize
     def original_filename; ""; end
     def content_type; "application/octet-stream"; end
     def path; @empty_file.path; end
+    def size; 0; end
+    def read; ""; end
   end
 
   def params(button)